International Concrete Abstracts Portal

Presents a conceptual model for the behavior of structural walls subjected to lateral load reversals. The primary feature of the model is a reduction in shear strength with increasing levels of deformation. Measured and calculated data from structural walls are evaluated to determine conditions for which the strength and deformation capacity of a wall may be limited by the residual shear strength.

An experimental program is summarized which is aimed at enhancing the knowledge base regarding seismic behavior, analysis, and design of precast concrete shearwalls. The "emulation design" and "jointed construction" philosophies are described and an idealization of the behavior of precast shearwalls presented. A compendium of connection details for precast concrete shearwalls, seven for vertical joints and four for horizontal joints, is selected for further study; the selection process is described. The connection details are proportioned for a prototype shearwall that is designed as part of a six-story precast concrete office building. A description of all connection details and test procedure is given. Highlights from the cyclic load tests of the vertical joint specimens are documented, including connection resistance, displacement response, initial stiffness, and energy dissipation capacity.

Members of earthquake-resisting reinforced concrete frames--such as beams, columns, joints, and anchorages--are designed on the basis of force demands. Detailing requirements are established from collected experimental observations of measures which are most effective in maximizing overall cyclic toughness of frame assemblies. In this paper, a displacement-based approach to evaluating detailing requirements for frame elements is presented. Expressions are derived for the participation of beams, columns, joints, and anchorages in overall story drift. Simple element models are presented for beam-column joints and anchorages; guidelines for conventional sectional analysis of beams and columns are given. With an assessment of the local demand in each element type and mechanical models of element behavior, it is demonstrated that member variables normally considered as part of detailing can be accounted for in a quantitative supply vs. demand fashion. A case study is made for an example in the ACI Committee 352 Recommendations to illustrate how a displacement-based frame evaluation is carried out and to provide a reference point for comparison with an existing design approach for beam-column joints.

Presents a review of (1) previous experimental studies on the earthquake response of square reinforced concrete columns and a discussion of their applicability to bridge columns in areas of moderate and high seismic risk; (2) confinement steel design for rectangular columns based on different codes and methods and an example column to compare these codes; and (3) two concrete confinement models in relationship to their application in estimating a range of displacement ductility for square columns, rectangular columns, and pier walls. The results of part (1) showed that previous tests on square columns are mostly under relatively large axial stresses which represent the state of building columns and that the data are generally aimed at areas of high seismic risk. Part (2) showed a considerable variation among different codes and methods in terms of the amount of lateral reinforcement and the parameters considered in design. The results of part (3) indicated that measured displacement ductilities were generally within a range calculated using the two confinement models selected in this study.

Presents nondestructive and destructive dynamic field testing and structural identification studies on actual constructed facilities. The specimens discussed here include a 27-story reinforced concrete (RC) flat-slab building, an RC slab bridge, two 80-year-old steel truss bridges, and three RC slab on steel girder bridges of various ages. The seismic vulnerability of the mid-rise building was evaluated and the test bridges rated by code procedures as well as by field-calibrated comprehensive 3-D FE models developed by structural identification. Experimentally measured and analytically simulated modal flexibilities of the bridges were correlated with deflections obtained under proof-load-level truck-load tests. The rating factors obtained by filed- calibrated models exceeded the corresponding operating rating factors by two and a half to four times for all of the test bridges. These studies revealed our capabilities for evaluating vulnerability or reliability of different classes of facilities. The bridge rating efforts helped to identify and conceptualize a number of unresolved important issues that influence bridge rating and management. Serviceability aspects that emerged as critical were studied through the relative contributions of different mechanisms to bridge deflections.